import sys
import json

def main():
    if (len(sys.argv) == 1):
        infile = sys.stdin
        outfile = sys.stdout
    elif (len(sys.argv) == 2):
        infile = open(sys.argv[1], 'rb')
        outfile = sys.stdout
    elif (len(sys.argv) == 3):
        infile = open(sys.argv[1], 'rb')
        outfile = open(sys.argv[2], 'wb')
    else:
        raise SystemExit((sys.argv[0] + ' [infile [outfile]]'))
    try:
        obj = json.load(infile)
    except ValueError, e:
        raise SystemExit(e)
    json.dump(obj, outfile, sort_keys=True, indent=4)
    outfile.write('\n')


if (__name__ == '__main__'):
    main()

